Denial of service attacks, including mail flooding, are common problems affecting the security of a mail transfer agent used in the management of electronic mail (e-mail). In the present state of the art, one possible response is to reject all incoming e-mail during a mail flooding or denial of service attack incident. However, such a response may be undesirable as e-mail from a legitimate sender can be rejected along with the mail flood from a problem sender. The present state of the art does not provide a method of distinguishing between the problem sender and the legitimate sender during periods of high e-mail activity.
What is needed is a method for responding to incoming e-mail which selectively rejects e-mail from a problem sender and selectively accepts e-mail from a legitimate sender during the onset of mail flooding or denial of service attack.